Battery life is a critical component in today's world of portable electronics, particularly in wireless communications. It is not uncommon for business persons to carry and use multiple devices such as personal digital assistant (PDA), cellular telephone, two-way radio transceiver, or the like, which often connect and interact with one other via both wired and wireless interfaces. As users continue to use more of these portable battery-powered devices, battery power management methods that respond to the needs of the overall “system” of devices become more important. In the past, the power for all of these devices has been managed individually, which can be burdensome on the user to keep these devices all sufficiently charged and operational.
Most existing portable battery-powered devices use their rechargeable batteries in one of two modes: either a charging mode while the device is not in use or discharging mode where the battery is discharged while the device is being used. When a user has multiple devices that each have their own battery and power management systems, the user runs the risk of discharging the battery of one device at a faster rate than the other devices. For example, if a person has both a cell phone and PDA, it is possible to completely drain the battery thus rendering the cell phone unusable, while the PDA still has a full charge. In systems where the devices can be physically connected to one another either during use or periods of inactivity, it would be advantageous to have a system that is capable of managing the collective power of each device in the system.
In addition, the prior art includes power management systems capable of sharing power between multiple connected devices. However, such systems do not operate intelligently for the benefit of the overall “system.” For example, many cell phones often come with a universal serial bus (USB) cable for connecting to personal computers. The cell phone may be charged by the computer while connected via the USB cable. While the cell phone is connected to a laptop is an example of two battery-powered devices sharing power, this scenario is not a method of managing the power of an entire system. This is simply a one-way power charging method (from laptop to cell phone) and does not take into consideration the use of a device having a greater percentage of charge remaining. The example is a simplistic system that automatically charges the phone while it is connected, regardless of the available power of the laptop or cell phone.
Thus, the need exists for a power management system that can utilize the battery charge of multiple individual devices for power management of all electrical devices connected to it.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.